Our long-term goal is to understand the genetic and molecular elements that determine the process of aging and life span. The aim of this proposal is to test how specific genes and proteins affect the life span extension seen with caloric restriction. Studies of caloric restriction show changes in a large number of genes and physiological systems. One of these, the Rpd3/Sir2 pathway, has been implicated in life span extension in yeast, nematodes, and flies. A prerequisite to developing molecular genetic and pharmacological interventions that extend life span through the manipulation of the caloric restriction/Rpd3/Sir2 pathway is a better understanding of the pathway and the genes and proteins that are regulated by it. In this proposal we will confirm the importance of Sir2 in the caloric restriction pathway in flies, define the position of Sir2 within the pathway relative to Rpd3, determine the timing and site of tissues important for its action on longevity, and examine the effect of small exogenous molecules known to increase Sir2 activity on longevity. Using our fly model system we will then examine the role in life span extension of p53, a transcription factor and tumor suppressor in mammals whose activity is controlled by Sir2. Finally, we will use a comparative microarray analysis to identify genes and proteins important in effecting longevity in the Rpd3/Sir2/caloric restriction pathway in flies and initiate a genetic analysis of the potential effector molecules.